Static control problems have been recognized and routinely addressed for years in the electronic manufacturing industries. As the miniaturization of electrical equipment progresses and the growth of the electronic industry continues, static control problems have become more and more a subject of serious concern to the electronic industry. To put the problem into perspective, it is known that someone walking across a carpeted floor can accumulate more than 30,000 volts of static charge, while published literature has referred to 25 to 100 volts as critical static discharges which could cause immediate and catastrophic damage to a sensitive electronic chip. This demonstrates the need for protecting the areas and environments where sophisticated electronics equipment are manufactured and stored.
It has been generally recognized that the prevention of static discharge requires that the total manufacturing and storage environment be constructed of materials which are capable of dissipating static charges, and that these materials be connected to a common ground. In such an environment, it is critically important that surfaces, in general, and the flooring structure, in particular, be protected against electrostatic discharge.
It has long been known that polymeric materials, of the kinds typically employed in floor coverings, such as polyvinyl chloride, are normally insulative. They can be made conductive, however, by incorporating either a conductive filler or an antistatic agent in the polymer structure or by employing both methods at the same time. When conductive fillers, such as metallic materials or carbon blacks, are used, the filler concentrations required to impart conductivity to the polymer structure are usually relatively high, typically thirty to fifty percent by volume. At such concentrations, the appearance of the polymeric structure is usually black, gray, or brown, depending upon the materials employed, and are not suitable for highly decorative floor covering applications.
To protect a floor covering from accumulating dirt and to improve the lustre or glossiness of a floor covering, a floor polish is often used as a maintenance aid. For most commercial conductive floor tiles or sheet materials, especially those made with carbon and other metallic materials, i.e., commercially available carbon veined tiles and the like, such maintenance aids are not recommended by the manufacturers. This is because most commercially available floor polish materials are insulative. They will interfere with the conducting path formed by the carbon particles, or other metallic materials therein, affecting the ability of the conductive floor covering to dissipate static charges.
For similar reasons, even a conductive floor polish is often not recommended for use in the maintenance of conductive floors, such as those employing carbon-veined tiles. This is typical because the conductive floor polish is not usually as conductive as the conductive floor covering itself. In addition, the residual polish worn away by traffic also interferes with the conducting path, further decreasing the charge dissipative efficiency of the conductive floor covering.
Antistatic agents, such as those containing quaternary ammonium salt functionalities have been known to impart charge dissipative properties to floor coverings in the past. However, these antistatic materials are sensitive to moisture and, in previous uses, have affected the manufacturing processing characteristics and performance characteristics of the floor coverings in which they were employed. For example, a floor covering containing moisture absorptive materials might swell or grow in length where water is present. If the moisture growth is high, the floor covering might curl or buckle, causing what is commonly referred to as a peak-seam in an installed floor covering. High moisture growth is, therefore, generally considered to be a high risk with respect to the performance of floor coverings, particularly when installed on on-grade or below-grade concrete sub-floors.
Further, the antistatic properties of the prior art surface coverings, in particular floor coverings, are relatively short lived. The antistatic agents of the prior art floor coverings tend to migrate and are removed from the floor surface by conventional cleaning procedures. In as short a period as one or two years, the antistatic property of a floor covering is markedly reduced.